Facile fabrication of porous polymer fibers via cryogenic electrospinning system

Porous fibers had better performance in many application fields for their larger surface area or extra nano topography than smooth ones. However, high vapor pressure solvents or selective removal of one phase from fastidious blended fibers were mostly used to fabricate porous fibers in electrospinning process, which made the process unfriendly and inconveniently. Here, a facial process on fabrication of porous fibers was developed by integrating the principles of thermally induced phase separation with the self-made cryogenic electrospinning system (CES) which can provisional solidify the polymer jet on the freezing collector. For demonstration, the polymer solution of Polycaprolactone (PCL) with solvent of glacial acetic acid was chosen. The PCL porous fibers with diameter of 3.29 ± 0.42 μm were successfully prepared at the height of 90 mm and freezing temperature of −3.6 ± 0.3℃ on collector in room environment. Furthermore, the pores on the surface of fibers exhibited two types: pits and polygon concaves. The pits were induced by phase separation at freezing temperature and the polygon concaves were due to the interaction of residual solvent with ice crystals on surface of silicon wafer or metal collector recruited from the air moisture. Generally, this process was suitable to polymer solutions with solvents of low vapor pressure but high freezing point.